Occasionally it may be necessary to determine the various times of a file.
These times break down to access (when the file was last accessed),
modification (time of last modification), and inode (time of last
modification of the inode (mode / permission changes, etc.). FreeBSD,
Solaris, and Linux have various means of determining this information,
one of which being /bin/ls. The output from this command is nearly
identical for these OS types:
host [0] /bin/ls -lt /etc/passwd
-r--r--r-- 1 root sys 865 Mar 8 15:38 /etc/passwd
The option, -t, specifies to display the time of the last modification
of the file. (This is the default timestamp printed when only the -l
option is specified.)
host [0] /bin/ls -lu /etc/passwd
-r--r--r-- 1 root sys 865 Aug 4 01:23 /etc/passwd
The option, -u, specifies to display the time of the last access to the
file, perhaps for a read, etc.
host [0] /bin/ls -lc /etc/passwd
-r--r--r-- 1 root sys 865 Aug 4 16:33 /etc/passwd
The option, -c, specifies the displaying of the inode modification time,
which may be impacted by things such as changing the files permissions,
the initial creation of the file, if a directory, the adding of files,
etc. It should be noted that while the inode time is set at the time of
a file's creation, it should not be relied upon as the creation time as
the inode time can easily be changed following any number of activities.
Also of note, the -l option is necessary in each command as otherwise
the output expected is not visibly printed to STDOUT.
A means of determining all three of these times at once on FreeBSD exists
in the stat command:
bsdhost [0] /usr/bin/stat -x /etc/passwd
File: "/etc/passwd"
Size: 1627 FileType: Regular File
Mode: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ wheel)
Device: 4,14 Inode: 71000 Links: 1
Access: Sun Jul 30 01:14:02 2006
Modify: Thu Jun 22 14:19:44 2006
Change: Fri Aug 4 16:38:58 2006
The -x operand simply tells stat to "Display information in a more
verbose way as known from some Linux distributions."
Speaking of Linux and quite similar to the FreeBSD output:
linhost [0] /usr/bin/stat /etc/passwd
File: `/etc/passwd'
Size: 1814 Blocks: 8 IO Block: 4096 regular file
Device: 801h/2049d Inode: 952083 Links: 1
Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root)
Access: 2006-08-10 21:58:21.000000000 -0400
Modify: 2006-08-04 21:12:46.000000000 -0400
Change: 2006-08-04 21:12:46.000000000 -0400
On Solaris, a slightly more obscure method exists via truss, providing
essentially the same information as the FreeBSD or Linux stat commands:
sunhost [0] /usr/bin/truss -vlstat -tlstat ls -l /etc/passwd
lstat64("/etc/passwd", 0x08046930) = 0
d=0x00D80040 i=288 m=0100644 l=1 u=0 g=3 sz=751
at = Aug 4 16:39:36 EDT 2006 [ 1154723976 ]
mt = Jul 11 16:05:18 EDT 2006 [ 1152648318 ]
ct = Aug 4 16:42:30 EDT 2006 [ 1154724150 ]
bsz=8192 blks=2 fs=ufs
-rw-r--r-- 1 root sys 751 Jul 11 16:05 /etc/passwd
The operands of -tlstat and -vlstat tells truss to trace specifically the
lstat system call and to be verbose about said tracing (respectively).
The "ls -l" is the specific command in which truss is following.
